A voltage follower circuit is conventionally known as a buffer amplifier. The conventional circuit, shown in FIG. 1, maintains the output voltage level by grounding the source of a MOSFET transistor through resistor R1. When the value of R1 is small, the level of the output voltage is lowered. When the value of R1 is large, the output voltage Vout follows the input poorly because of the increase of the time constant associated with parasitic capacitance C1.